This disclosure relates to latex coating compositions, in particular latex compositions comprising a carboxy ester ketal, methods for the manufacture of the compositions, and uses of the compositions.
Latex coating resins are water-borne emulsions of sub-micrometer polymer particles. The emulsions are formed by emulsion polymerization, and then can be further formulated for a variety of applications, for example latex paints, caulks, sealants, adhesives, mastics, and inks Latex coating compositions, can be formulated with a variety of additives, among them a coalescing solvent or “coalescent.” Coalescing solvents promote film formation. The coalescing solvent serves as a plasticizer, softening the resin particles by reducing the glass transition temperature (Tg) of the particles, and enabling them to fuse into a continuous film. For example, a latex paint composition containing a coalescing solvent is coated on a substrate and then cures by coalescence, where the water and the coalescing solvent evaporate sequentially or simultaneously. During evaporation, the coalescing solvent softens the latex polymer binder particles, fusing them together into an entangled polymer film so that the polymer binder will not redissolve in the water/solvent that originally carried it.
Coalescing solvent selection is guided by considerations such as solubility, reactivity, volatility, toxicity, environmental profile, and cost. While a number of solvents are available and in commercial use, there remains a need in the art for new solvents that offer a favorable combination of these characteristics. Further, there is an increasing desire for “bio-sourced” solvents that can be used as replacements for petroleum-sourced solvents. Few bio-source solvents are available that can meet the increasingly demanding technical requirements for latex coating compositions and coatings, including paints, sealants, adhesives, mastics, and inks Even where such solvents are available, the solvents can have various drawbacks. For example, ethanol is a versatile solvent that is readily available from bio-based sources, but its high flammability and high volatility limits its use in many applications. A further drawback of many bio-sourced solvents is that the chemical and physical properties of the solvents can only be adjusted to a limited extent.